Device for monitoring the level of the condensate collected in the measuring cylinder of a standardized distillation apparatus and method implemented by using this device

Abstract

Device for monitoring the level of the condensate collected in the measurement cylinder of a standardized distillation apparatus for automatically distilling liquid specimens, characterized in that it comprises: on the one hand, a double optical barrier emitting a central beam centered on the measurement cylinder ( 1 ), so as to allow detection of the part below the meniscus, and an eccentric beam offset with respect to the central beam and located close to the wall of the measurement cylinder ( 1 ), so as to allow the part above the meniscus to be detected; and, on the other hand, a fixed optical barrier intended for counting the drops of condensate falling into the measurement cylinder ( 1 ) during distillation.

The invention claimed is: 
     
       1. A device for use in monitoring a level of condensate collected in a measuring cylinder of a distillation device for distilling liquid samples, comprising:
 an optical system, comprising:
 a first, dual optical barrier including first and second transmitter/receiver pairs each capable of transmitting a light beam, the light beams respectively directed horizontally through the measuring cylinder with the first and second transmitter/receiver pairs movable via a step motor to align the light beams with a meniscus of the condensate collected in the cylinder, the first transmitter/receiver pair transmitting a first, center light beam which is centered on the measuring cylinder and alignable with a lower portion of the meniscus and the second transmitter/receiver pair transmitting a second, eccentric light beam which is offset relative to the first, center light beam and which passes between the center and the wall of the measuring cylinder and is alignable with an upper portion of the meniscus; and 
 a second optical barrier including a third transmitter/receiver pair operable to detect and count drops of condensate which fall into the measuring cylinder. 
 
 
     
     
       2. A method, implementable by the device of  claim 1 , for determining a volume V of condensate collected in the measuring cylinder from the height of the lower portion of the meniscus using the equation:
     V=mX+b   (I)
 
 
       where m and b are parameters corresponding to a gradient and displacement, respectively, at an origin of a calibration line of the distillation device, X is a distance expressed as steps of linear driving via the step motor between a low reference position corresponding to the base of the measuring cylinder and the height of the lower portion of the meniscus, comprising the following steps:
 determining, in a preliminary calibration step, the parameters m and b of equation (I) to establish the calibration line of the distillation device and establish a height MH of the meniscus; 
 positioning the first optical barrier in the low reference position; 
 actuating the step motor to move the first optical barrier upward to allow the second, eccentric beam to detect and monitor a height of the upper portion of the meniscus; 
 calculating a volume V of condensate collected in the measuring cylinder using the equation:
     V=mY+b−MH   (II)
 
 
 
       where Y represents a distance expressed as steps of linear driving via the step motor between the low reference position and the height of the upper portion of the meniscus;
 monitoring the height of the upper portion of the meniscus and calculating the volume V in accordance with the equation (II) until the first, center beam detects the lower portion of the meniscus; 
 commutating the detection to monitor the lower portion of the meniscus using the first, center beam; and 
 calculating the volume V of condensate collected in the measuring cylinder using equation I with a correction corresponding to it volume of condensate collected in the measuring cylinder during said commutating step. 
 
     
     
       3. The method of  claim 2 , further comprising the following additional steps:
 introducing, during said determining step, at least two known volumes of sample V1 and V2 successively into the measuring cylinder; and 
 measuring corresponding distances X1, X2, Y1 and Y2. 
 
     
     
       4. The method of  claim 2 , wherein:
 said step of monitoring the height of the upper portion of the meniscus further comprises calculating an initial volume of drops of condensate falling into the measuring cylinder using the second optical barrier; and 
 said commutating and calculating steps further comprise calculating the volume V using the calculated initial volume. 
 
     
     
       5. The method of  claim 2 , further comprising the additional step of:
 monitoring the upper portion of the meniscus in the event the condensate becomes too opaque to detect the lower portion of the meniscus.